A Ubiquitous Sensor Network (USN) means attaching electronic tags to every required point, detecting the precise fundamental data of objects as well as nearby environment data such as temperature, humidity, pollution degree and crack data, connecting the data to network and managing the data. USN gives a computing or communicating function to all the objects to realize a ubiquitous environment to communicate at anytime, anywhere.
Such the USN grows from a Radio Frequency Identification (RFID) technology and develops into a network form by having a sensing function additionally.
The above RFID is a technology to receive and transmit data from an electronic tag attached to objects by using radio frequency.
An RFID system uses various frequency bands such as low frequency, high frequency, UHF, microwave, having different usages and practical uses respectively.
Among the bands, UHF is spreading over the whole field of living including distribution, logistics because it may transmit signals to the great distance.
FIG. 1 is a diagram showing the conventional RFID system.
Referring to FIG. 1, an RFID system 100 comprises an RFID reader 101 and an electronic tag 102. RFID reader 101 includes an internal or external antenna forming an electromagnetic field, that is, an RF field by diffusing an active signal. If the electronic tag 102 enters the RF field 105, the electronic tag 102 receives the active signal diffused by the antenna and transmits data stored at a tag to the RFID reader by using the received active signal. After this, the RFID reader 101 receives and analyzes the data transmitted by the electronic tag to acquire particular data on an object where the electronic tag is attached.
Also, the particular data acquired at the RFID reader 101 provides a base useful in distribution/logistics management such as distribution, fabrication, price fluctuations, marketing, etc.
Such RFID technology is expected to spread throughout various fields such as farming, medical service, aviation, distribution, logistics, manufacture, etc, according to a development of chip-manufacturing, minimization, wireless communication technology and various solution programs.
However, a propagation environment varies as factors such as location and velocity of the electronic tag in RFID reader's RF field, packing materials of tag-attached products (e.g. in case of pallet freight), etc. Differences of a data error rate, a stability or a read range arising from a variation of the propagation environment become a factor decreasing a recognition rate of an electronic tag and a reliability of an RFID system.
As above, technologies for improving a recognition rate of RFID reader by internal or external factors are under development.